Acoustic diaphragm and mounting



June 17, 1930. wm 1,763,876

ACOUSTIC DIAPHRAGM AND MOUNTING Filed Jan. 4, 1926 W INVENTOR PatentedJune 17, 1930 UNITED STATES NATHANIEL BALDWIN, OF EAST MILL CREEK, UTAHACOUSTIC DIAPHRAGM AND MOUNTING Application filed January 4, 1926.Serial No. 79,165.

The present invention appertains to acoustic diaphragms and particularlyto that class in which large diaphragms are used without horns for loudspeakers.

The principal objects of this inventioriare to provide an improveddiaphragm of the class commonly made in the form of a cone, to providean improved housing for the diaphragm, and to provide an improved meansof mounting said diaphragm.

I attain these and other objects by the mechanism illustrated in theaccompanying drawing in which Fig. 1 is a vertical section, showing theseveral features, and Fig. 2 is a front elevation showing the diaphragmand part of the mechanism used in mounting the same.

In the figures of the drawing numeral 1 designates the housing which maybe made preferably in the form of a cylinder. N11.- meral 2 designates aring which is secured to the inner surface of the housing 1, and at itsinner circumference is provided with a; projecting flange 3, which formsa seat for the diaphragm. The diaphragm, preferably made of paper orother like material, consists of an inner portion 4 which is reenforcedpreferably by being formed into a special shape, such as the cone shapeshown in the figure, an outer plain portion 5 which permits thenecessary movement of the central portion 4, and an edge portion 6 bentat right angles to the plain portion 5 and set into a reenforcing rim 7,made of a folded strip of metal or other suitable material. A short foldin the edge portion 6 of the diaphragm will enable the rim 7 to beclamped on with security. The rim 7 is somewhat larger in diameter thanthe flange 3 and when the diaphragm is placed against the flange 3 andforce is applied to the rim 7 to press the diaphragm against the flange,the diaphragm will e put under tension, according to the force appliedto the rim.

A suitable force against the rim 7, and uniformly distributed around itis obtained ,by means of an expansible ring 8, preferably a compressedsplral spring which presses against an inclined surface 9, on one sideof an annular groove formed in the inner wall of the housing 1, andagainst said rim. The housing may be conveniently made of sheet metal,in which case the groove will consist of an annular head in thematerial. If a spiral spring or some equivalent means is used as theexpansible ring 8, it will adjust itself to the expansions orcontractions of the diaphragm and maintain a proper tension of the same.

This diaphragm may be used for any of the purposes for which diaphragm'sare used, to receive sound or to reproduce it; but as here illustratedit is electrically operated and serves as a loud speaker. The apex ofthe cone is connected by a rod or cord 10 to an armature 11, which issecured to one pole of the permanent magnet 12. A polepiece 13surrounded by the actuating coil 14 is connected to the other pole ofthe permanent magnet 12 and approaches the armature 11. Themagnet 12 ismounted within the housing 1 by means of a screw and spacing block 15 asshown.

A convenient base for the instrument is formed by joining two pieces ofpressed or spun metal 16 and 17 and connecting them to the housing asillustrated.

I claim:

1. A diaphragm with-cone shaped inner portion and substantially plainouter portion with folded edge and a reenforcing rim consisting of aband folded over the folded edge of the outer portion.

2. A diaphragm with reenforcing rim, a housing for said diaphragm, anannular seat for said diaphragm secured to said housing,

an annular inclined surface in said housing, 1

and an expansible ring pressing against said inclined surface andagainst said rim and adapted to put tension on said diaphragm bypressing it against said seat.

3. A diaphragm with cone-shaped inner portion and substantially plainouter portion, a reenforcing rim consisting of a band folded over theedge of the outer portion, a cylindrical housing, for said diaphragm, anannular seat for said diaphragm secured to said housing, an annularinclined surface in said housing, and a compressed annular spiral springpressing against said inclined surface and against said rim and adaptedto put tension on said diaphragm by pressing it against said seat.

4:. In an acoustic device, a diaphragm having a folded periphery, ahousing 'within which said diaphragm is mounted, a reinforcing rimfolded over the folded periphery of said diaphragm, a seat for saiddiaphragm bearing thereagainst radially inwardly of said foldedperiphery and tension, means acting against the folded edge of saidreinforcing rim. v

5. In an acoustic device, a diaphra m having a folded periphery, ahousing or said diaphragm, a seat within said housing bearing againstsaid diaphragm radially inwardly of said periphery, a member undercompressive stress bearing against the said reinforcing rim, and asloping seat within which said stressed member is seated, the said seatsloping toward said reinforcing rim.

NATHANIEL BALDWIN.

